The present observation of Greenery Day (みどりの日, Midori no Hi) as a public holiday in Japan stems from the celebration of the birthday of the Emperor Shōwa (Hirohito, who lived from 1901 to 1989) on April 29 every year during the Shōwa era (1926 - 1989).
[1] Officially, as its name suggests, it is a day to commune with nature and to be thankful for blessings.
[2] However, in practice it is seen as just another day that expands the Japanese Golden Week vacation.
In 2007, Greenery Day moved to May 4, and April 29 was changed to Shōwa Day in accordance with a 2005 revision of the law pertaining to public holidays.
The Shōwa Emperor reigned for 62 years and 2 weeks.